1. Field of the Invention
The present invention relates generally to a port expansion system for connecting a single port, such as a USB port, on a host system such as a personal computer (PC) to various computer peripheral devices and functions, and particularly to such an expansion system that is user configurable so as to provide a high degree of flexibility and efficiency in the connection of the host system to a wide selection of peripheral devices and functions.
2. Description of the Prior Art
Although the invention and its background will be described chiefly in the context of the USB standard bus interface or protocol, it will be evident to those skilled in the art that the invention may be used with other standard bus interfaces including IEEE 1394, also called “Firewire” or “i.Link”, and SCSI.
The difficulty of connecting and properly operating the many different kinds of personal computer peripheral devices and functions such as printers, scanners, digital cameras, modems, disk drives, and so forth, led to the adoption of the Universal Serial Bus (USB) standard which provides a hot pluggable, “plug and play”, cascadable serial interface using a low cost standard socket for adding external peripheral devices and functions. The Universal Serial Bus Specification Rev. 1.1 dated Sep. 23, 1998 is incorporated herein by reference in its entirety. Because power as well as data are transmitted through USB cables, some low power devices can be operated without the need for separate power adapters. The USB specification allows up to 127 peripheral devices to be connected to a single PC using USB hubs and defines how these peripheral devices can be connected together so that a host can use the resources provided by each device. USB ports are already found on many new PCs and a wide variety of USB peripherals are already on the market. Legacy-free PCs with one or perhaps two USB ports to connect peripherals are also becoming available. Such PCs do not incorporate traditional, standard interfaces.
There are currently available numerous converters for connecting a USB port on a PC or USB hub to traditional interfaces including serial ports, parallel ports, RJ-45 Ethernet LAN ports, and RJ-11 modem ports. These converters may also include one or more USB ports. However, the converters are housed within individual enclosures requiring a separate cable to attach each enclosure to a host system or to a hub.
Also presently available are multifunction USB hubs. For example, one such multifunction hub expands a USB-enabled PC to provide four additional USB ports along with three traditional ports consisting of two serial ports and one parallel printer port. However, such a multifunction USB hub is integrated into a single housing so that only a fixed number and combination of peripheral device or function ports is made available.